The Immunotoxicity of Workplace Xenobiotics interagency agreement functions to enhance the immunotoxicological evaluations on humans exposed to quantifiable levels of xenobiotics in the environment and workplace. Exposure to fungi is of growing concern in the general population, particularly in children, causing asthma and rhinitis. This exposure results from home and school environments associated with condensation, visible mold, moldy odor, and water-induced damage. Certain worker populations are also at elevated risk for fungal exposures including agriculture and horticultural workers from handling of moldy farm and bio-waste products in agricultural facilities, wood processing workers, office workers or school staff in water-damaged buildings as well as construction and remediation workers who handle moldy building materials. Although fungal exposure has often been associated with allergic, toxic and/or infectious health effects, the actual potential of different fungi to cause or aggravate such adverse effects remains unclear. Establishing exposure-response relationships for health effects of working in indoor environments with microbial contamination has been hampered by the lack of relevant microbial exposure assessment. In particular, health effects associated with fungal toxin (mycotoxin) exposure in the indoor environment are an understudied problem. Newer, chemical-based methods, including the use of gas chromatography-tandem mass spectrometry (GC-MSMS) and ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MSMS), for measuring microbial cell-wall components and toxins are being developed, but still are not readily available. The National Academy of Sciences has recognized the need to develop better fungal exposure assessment methods as a high research priority and the NTP has a major initiative for studying the health effects of fungal exposure. This project applies and modifies recently developed GC-MSMS and UPLC-MSMS methods to quantify fungal toxins in environmental samples from water damaged buildings for which we have existing data on other fungal and bacterial components as well as health questionnaire data on building occupants. The knowledge gained from these studies will also address specific NIOSH and NIEHS research goals for reducing environmental and occupational causes or contributing factors to acute and chronic illness and disease in worker populations as well as children.